DESCRIPTION: Williams syndrome is a rare congenital neurodevelopmental disorder which is characterized at the psychological level by an unusual cognitive phenotype. Individuals with Williams syndrome are typically affectionate, very interested in people, and have relatively good language and face-processing skills, despite low IQ scores. This profile has led some researchers to propose that Williams syndrome involves a sparing in theory of mind abilities. The research program will explore theory of mind and related social-cognitive abilities in well- defined groups of children and adolescents with Williams syndrome. The subjects with Williams syndrome will be compared to two sets of mentally retarded/low IQ (MR) and normal controls: one set matched on overall mental age, the other set matched on language abilities. The main hypothesis is that the subjects with Williams syndrome will perform significantly better than the matched MR subjects on tasks tapping basic theory of mind abilities, including false belief (Experiments 1, 2), knowledge and intention (Experiment 4), the use of mental states to explain behavior (Experiment 3), discrimination of facial expressions of affect (Experiment 6), and visual perspective taking (Experiment 5). Subjects with Williams syndrome are also predicted to perform significantly better than the MR controls on a second-order theory of mind task (Experiment 7). In contrast, subjects with WIlliams syndrome are predicted to perform at the same level as the MR controls, and significantly worse than the normally developing controls, on tasks tapping higher-order social-cognitive constructs that build on a basic theory of mind but which also entail additional aspects of conceptual change. This prediction will be tested in tasks tapping knowledge of lies and jokes (Experiment 8), the concepts of trait (Experiment 9) and empathy (Experiment 11), moral judgment (Experiment 10), concepts of personal and social relations (Experiment 12), and self understanding (Experiment 13). The findings from this research will have important theoretical implications for conceptualizations of the cognitive and neural mechanisms that underlie social cognition, and will advance the understanding of social development in individuals who have Williams syndrome.